What is HHT???

This is taken off of the HHT website, I wanted to just share the most basic explanation that I could find out there and share that you all.

HHT is a genetic disorder that causes abnormalities of blood vessels. Most blood vessels in the body of someone with HHT are normal. However, a small percentage of the blood vessels in a person with HHT have a specific type of abnormality. Abnormally formed blood vessels (telangiectasia and arteriovenous malformations) cause all the symptoms of HHT.

Blood vessels are the tubes that carry blood around our bodies. There are two types of blood vessels: arteries and veins. Arteries carry blood under high pressure out to all areas of the body after being pumped by the heart. Veins carry blood that should be under low pressure, back to the heart. An artery does not usually connect directly to a vein. Usually there are very small blood vessels called capillaries that connect an artery to a vein.

A person with HHT has a tendency to form blood vessels that lack the capillaries between an artery and vein. This means that arterial blood under high pressure flows directly into a vein without first having to squeeze through the very small capillaries. This place where an artery is connected directly to a vein tends to be a fragile site that can rupture and result in bleeding. We usually call a blood vessel that is abnormal in this way a telangiectasia (tel-AN-jee-eck-TAZE-ee-ya), if it involves small blood vessels. We tend to call it an arteriovenous malformation (AVM) if involves larger blood vessels. So, an AVM might be thought of as a big telangiectasia. The basic abnormality in the blood vessel is the same.

Telangiectases tend to occur at the surface of the body such as the skin and the mucous membrane that lines the nose. AVMs tend to occur in the internal organs of the body. The telangiectases (plural for telangiectasia) and AVMs of HHT occur primarily in the nose, skin of the face, hands, and mouth and the lining of the stomach and intestines (GI tract), lungs, liver and brain. It is not currently known why these abnormal blood vessels tend to occur in certain parts of the body and not others.

An abnormal gene on either chromosome 9 or 12 causes most HHT. The gene on chromosome 9 is called endoglin and the gene on chromosome 12 is called activin-like kinase 1 (ALK-1). Any particular individual or family will have only one of these two genes appear abnormal. Normally, these genes produce a substance that is involved in the formation of blood vessels. Because of an abnormality in one of these genes, individuals with HHT make less of one of these substances. This, in turn, can interfere with the normal formation of a blood vessel.

The abnormal HHT gene is usually inherited from one parent who has HHT. HHT is a "dominant" disorder, meaning it only takes one abnormal copy of the gene, from only one parent, to cause the disorder. Each child of a parent with an HHT gene has a 50% chance of inheriting this abnormal gene. If a particular child does not inherit the HHT gene from his or her parent, he/she has no chance to pass the HHT gene to a child or grandchild. The gene does not skip generations! However, sometimes it can appear to skip because an individual with an HHT gene has symptoms that are so mild that they aren’t recognized, or if recognized are not correctly attributed to HHT. Very rarely in HHT, a genetic accident (new mutation) occurs in a sperm or egg cell of an unaffected parent and causes HHT in the child. But in most cases, the abnormal HHT gene has been in the family for generations.

Approximately 1.2 million people world-wide have Hereditary Hemorrhagic Telangiectasia (HHT). There is one statistic on the website that says there are 2 people born a day with HHT. So, HHT is uncommon, but not rare. There are more out there, but they are undiagnosed or misdiagnosed. That is a big problem, because thankfully the things that you CAN do to be healthy with HHT are preventitive measures, you have to know what is going on to treat it, keep it under control.

In my next post I will share some of the symptoms of HHT, the procedures that are performed to ensure the quality of life for people with HHT, and some personal stories of what my family has had done and what they live with.
God bless.